Merge pull request #2 from special/master

Fix crash when creating and deleting telepathy accounts directly
[telepathy-sasl-signon] Use libsailfishkeyprovider to load privileged oauth2 data
[telepathy-sasl-signon] Disable signon user interaction and password requests

This will be replaced by an API to trigger authentication failed
notifications and have the user reauthenticate via the normal UI.
[telepathy-sasl-signon] Set CredentialsNeedUpdate flag after failed login